Hydroxyurea Dose Escalation for Sickle Cell Anemia in Sub-Saharan Africa

Fostering a healthier generation of children with sickle cell disease through advancements in care

Sickle cell disease (SCD) is an inherited disorder of hemoglobin that affects tens of millions of individuals worldwide. Without preventive and disease-modifying therapy, SCD results in many acute and chronic complications impacting both quality and length of life. We are currently in a new generation of SCD care in high resource settings due to recent advancements in care. Universal newborn screening (NBS) for SCD with associated parental education and preventive care significantly improved mortality rates. Beginning in the 1990s, hydroxyurea emerged as a promising pharmacologic treatment for SCD due to its ability to increase the amount of fetal hemoglobin. It is now the mainstay of treatment, with strong recommendations to begin as early as the first year of life with the goal of reducing most short- and long-term complications and allowing for a normalized quality of life. More recently, gene therapy has come to the forefront in SCD and brings the hope of a cure for many patients. In 2023, the FDA approved two cell-based gene therapies for patients with SCD. The future is bright for patients with SCD, and the current generation of affected children will expectantly be able to grow up free of suffering and severe, frequent pain.

Susceptibility to childhood sepsis, contemporary management, and future directions

Sepsis disproportionally affects children across all health-care settings and is one of the leading causes of morbidity and mortality in neonatal and paediatric age groups. As shown in the first paper in this Series, the age-specific incidence of sepsis is highest during the first years of life, before approaching adult incidence rates during adolescence. In the second paper in this Series, we focus on the unique susceptibility of paediatric patients to sepsis and how the underlying dysregulated host response relates to developmental aspects of children's immune system, genetic, perinatal, and environmental factors, and comorbidities and socioeconomic determinants of health, which often differ between children and adults. State-of-the-art clinical management of paediatric sepsis is organised around three treatment pillars-diagnosis, early resuscitation, and titration of advanced care-and we examine available treatment guidelines and the limitations of their supporting evidence. Serious evidence gaps remain in key areas of paediatric sepsis care, especially surrounding recognition, common interventions, and survivor support, and to this end we offer a research roadmap for the next decade that could accelerate targeted diagnostics and personalised use of immunomodulation. However, improving outcomes for children with sepsis relies fundamentally on systematic quality improvement in both recognition and treatment, which is the theme of the third paper in this Series. Digital health, as shown in the fourth and final paper of this Series, holds promising potential in breaking down the barriers that hinder progress in paediatric sepsis care and, ultimately, global child health.

Rationale, Development, and Validation of HdxSim, a Clinical Decision Support Tool for Model-Informed Precision Dosing of Hydroxyurea for Children with Sickle Cell Anemia

Hydroxyurea treatment for children with sickle cell anemia (SCA) is effective and life-saving. Stepwise escalation to maximum tolerated dose (MTD) provides optimal benefits, but is logistically challenging and time-consuming, especially in low-income countries where most people with SCA live. Model-informed precision dosing (MIPD) of hydroxyurea expedites MTD determination and improves outcomes compared with trial-and-error dose adjustments. HdxSim, a user-friendly, online, clinical decision support tool was developed to facilitate hydroxyurea MIPD and evaluated using real-world pharmacokinetic (PK) data. First-dose hydroxyurea PK profiles were analyzed from two clinical trial datasets (Hydroxyurea Study of Long-Term Effects (HUSTLE), NCT00305175 and Therapeutic Response Evaluation and Adherence Trial (TREAT), NCT02286154). Areas under the concentration-time curve (AUC) estimated by HdxSim were compared with those determined using traditional trapezoidal methodology and PK software (MWPharm-DOS). The doses predicted by HdxSim and MWPharm-DOS were compared with the observed clinical MTD. For HUSTLE participants, HdxSim accurately estimated hydroxyurea AUC compared with the trapezoidal method, with < 20% variance. The average (mean ± SD) AUC for TREAT participants estimated with HdxSim (68.6 ± 18.0 mg*hour/L) was lower than MWPharm-DOS (78.6 ± 20.7 mg*hour/L, P = 0.012), but the average recommended doses were not different (425 vs. 423 mg/day, P = 0.97). Moreover, HdxSim was non-inferior to MWPharm-DOS at predicting clinical MTD (absolute difference 3.9 ± 5.8 vs. 4.9 ± 8.2 mg/kg/day, P = 0.19). HdxSim accurately estimates hydroxyurea exposure and is noninferior to traditional PK approaches at predicting the clinical hydroxyurea MTD. Hydroxyurea dosing based on target exposure leads to improved outcomes in children with SCA, and has the potential to make PK-guided hydroxyurea dosing more accessible to this neglected population globally.

Clinical Practice Patterns in Sickle Cell Disease Treatment: Disease-modifying and Potentially Curative Therapies

Therapeutic options for sickle cell disease (SCD) have increased recently as well as the development of updated national guidelines. It is not known how these options are being offered or to what degree guidelines are incorporated into clinical practice. This study aimed to describe practice patterns for pediatric hematologists regarding the use of disease-modifying and potentially curative therapies for SCD. A 9-section, cross-sectional electronic survey was disseminated during a 3-month period via SurveyMonkey, to members of the American Society of Pediatric Hematology/Oncology Hemoglobinopathy Special Interest Group (ASPHO HSIG). A total of 88 physician members of the ASPHO HSIG were surveyed. Ninety percent of respondents (72/80) start hydroxyurea routinely in patients with HbSS and HbSβ 0 thalassemia, regardless of disease severity. Laboratory monitoring was recommended every 3 months for stable dosing in 63.8% (51/80). New therapies were recommended for patients on hydroxyurea who were still experiencing SCD complications: L-glutamine 68.5% (37/54) or crizanlizumab 93.1% (54/58). Voxelotor was recommended for patients on hydroxyurea with low hemoglobin in 65.1% (43/66) of cases. Matched sibling transplant was considered for any disease severity by 55.1% (38/69). Gene therapy trials are offered on-site by 29% (20/69). Our study demonstrated the enhanced utilization of hydroxyurea while revealing the unexplored potential of other disease-modifying therapies in SCD. These findings underscore the importance of continued knowledge acquisition about the long-term efficacy of new medical therapies and addressing barriers to the use of proven therapies and guide the development of future studies of optimal SCD management.

Pharmacokinetic-Guided Hydroxyurea to Reduce Transfusions in Ugandan Children with Sickle Cell Anemia: Study Design of the Alternative Dosing And Prevention of Transfusions Trial

INTRODUCTION

People with sickle cell anemia (SCA) may require frequent blood transfusions to treat acute and chronic complications. Hydroxyurea is a life-saving treatment for SCA that could also decrease the need for blood transfusions. Inadequate medication access and challenges in dose optimization limit the widespread use of hydroxyurea in Africa. If feasible, pharmacokinetic (PK) dosing might improve dose determination to minimize toxicities and maximize clinical benefits. The Alternative Dosing And Prevention of Transfusions (ADAPT, NCT05662098) trial will analyze the impact of hydroxyurea on transfusion rate and serve as a pilot study to evaluate the feasibility of PK-guided hydroxyurea dosing in Uganda.

METHODS

Herein we describe the rationale and design of ADAPT, a prospective cohort study of ∼100 children with SCA in Jinja, Uganda. The primary hypothesis is that hydroxyurea will decrease blood transfusion use by ≥ 50%, comparing the transfusion incidence rate ratio between a 3-month pretreatment and a 12-month treatment period. A key secondary hypothesis is that our PK-dosing approach will generate a suitable hydroxyurea dose for ≥80% of participants. Every ADAPT participant will undergo hydroxyurea PK testing, and if a dose is generated within 15-35 mg/kg/day, participants will start on their individualized dose. If not, they will start on a default dose of 20 mg/kg/day. Hydroxyurea dose optimization will occur with periodic dose adjustments.

CONCLUSION

Overall, demonstrating the reduction in blood transfusion utilization with hydroxyurea treatment would provide leverage to increase hydroxyurea access, and PK-guided hydroxyurea dosing should optimize the safe and effective treatment of SCA across sub-Saharan Africa.

Hydroxyurea dose optimisation for children with sickle cell anaemia in sub-Saharan Africa (REACH): extended follow-up of a multicentre, open-label, phase 1/2 trial

BACKGROUND

Realizing Effectiveness Across Continents with Hydroxyurea (REACH) is an open-label non-randomised trial of hydroxyurea (hydroxycarbamide) in children with sickle cell anaemia in sub-Saharan Africa. The short-term results of REACH on safety, feasibility, and effectiveness of hydroxyurea were published previously. In this paper we report results from extended hydroxyurea treatment in the REACH cohort up to 8 years.

METHODS

In this open-label, non-randomised, phase 1/2 trial, participants were recruited from four clinical sites in Kilifi, Kenya; Mbale, Uganda; Luanda, Angola; and Kinshasa, Democratic Republic of Congo. Eligible children were 1-10 years old with documented haemoglobin SS or haemoglobin Sβ zero thalassaemia, weighing at least 10 kg. Participants received fixed-dose hydroxyurea of 17.5 (±2.5) mg/kg per day for 6 months (fixed-dose phase), followed by 6 months of dose escalation (2·5-5·0 mg/kg increments every 8 weeks) as tolerated, up to 20-35 mg/kg per day (maximum tolerated dose; MTD), defined as mild myelosuppression. After the MTD was reached, hydroxyurea dosing was optimised for each participant on the basis of changes in bodyweight and laboratory values over time (MTD with optimisation phase). After completion of the first 12 months, children with an acceptable toxicity profile and favourable responses were given the opportunity to continue hydroxyurea until the age of 18 years. The safety and feasibility results after 3 years has been reported previously. Here, haematological responses, clinical events, and toxicity rates were compared across the dosing phases (fixed-dose hydroxyurea vs MTD with optimisation phase) as protocol-specified outcomes. REACH is registered on ClinicalTrials.gov (NCT01966731) and is ongoing.

FINDINGS

We enrolled 635 children between July 4, 2014, and Nov 11, 2016. 606 children were given hydroxyurea and 522 (86%; 266 [51%] boys and 256 [49%] girls) received treatment for a median of 93 months (IQR 84-97) with 4340 patient-years of treatment. The current (Oct 5, 2023) mean dose is 28·2 (SD 5·2) mg/kg per day with an increased mean haemoglobin concentration (7·3 [SD 1·1] g/dL at baseline to 8·5 [1·5] g/dL) and mean fetal haemoglobin level (10·9% [SD 6·8] to 23·3% [9·5]) and decreased absolute neutrophil count (6·8 [3·0] × 109 cells per L to 3·6 [2·2] × 109 cells per L). Incidence rate ratios (IRR) comparing MTD with fixed-dose hydroxyurea indicate decreased vaso-occlusive episodes (0·60; 95% CI 0·52-0·70; p<0·0001), acute chest syndrome events (0·21; 0·13-0·33; p<0·0001), recurrent stroke events (0·27; 0·07-1·06; p=0·061), malaria infections (0·58; 0·46-0·72; p<0·0001), non-malarial infections (0·52; 0·46-0·58; p<0·0001), serious adverse events (0·42; 0·27-0·67; p<0·0001), and death (0·70; 0·25-1·97; p=0·50). Dose-limiting toxicity rates were similar between the fixed-dose (24·1 per 100 patient-years) and MTD phases (23·2 per 100 patient-years; 0·97; 0·70-1·35; p=0·86). Grade 3 and 4 adverse events were infrequent (18·5 per 100 patient-years) and included malaria infection, non-malarial infections, vaso-occlusive pain, and acute chest syndrome. Serious adverse events were uncommon (3·6 per 100 patient-years) and included malaria infections, parvovirus-associated anaemia, sepsis, and stroke, with no treatment-related deaths.

INTERPRETATION

Hydroxyurea dose escalation to MTD with dose optimisation significantly improved clinical responses and treatment outcomes, without increasing toxicities in children with sickle cell anaemia in sub-Saharan Africa.

FUNDING

US National Heart, Lung, and Blood Institute and Cincinnati Children's Research Foundation.

Association of ZBTB38 gene polymorphism (rs724016) with height and fetal hemoglobin in individuals with sickle cell anemia

Objectives

Our study evaluated the association of the polymorphism rs724016 in the ZBTB38 gene, previously associated with height in other populations, with predictors of height, clinical outcomes, and laboratory parameters in sickle cell anemia (SCA).

Methods

Cross-sectional study with individuals with SCA and aged between 3 and 20 years. Clinical, laboratory, molecular, and bone age (BA) data were evaluated. Levels of IGF-1 and IGFBP-3 were adjusted for BA, target height (TH) was calculated as the mean parental height standard deviation score (SDS), and predicted adult height (PAH) SDS was calculated using BA.

Results

We evaluated 80 individuals with SCA. The homozygous genotype of the G allele of rs724016 was associated with a lower height SDS (p < 0.001) and, in a additive genetic model, was negatively associated with HbF levels (p = 0.016). Lower adjusted IGF-1 levels were associated with co-inheritance of alpha-thalassemia and with the absence of HU therapy. Elevated HbF levels were associated with a lower deficit in adjusted growth potential (TH minus PAH).

Conclusion

Our analysis shows that SNP rs724016 in the ZBTB38 is associated with shorter height and lower HbF levels, an important modifier of SCA.

Prevalence of Duffy null and its impact on hydroxyurea in young children with sickle cell disease in the United States

Consistent with studies showing a high prevalence of the Duffy null phenotype among healthy Black Americans, this retrospective study found that Duffy null was present in >75% of a young and contemporary cohort of children with sickle cell disease (SCD) in the United States. Despite the potential for this phenotype to impact absolute neutrophil counts, hydroxyurea (HU) dosing, and outcomes, it was not associated with being prescribed a lower HU dose or having increased acute SCD visits early in the HU treatment course. Future studies are needed to confirm these findings in older children with SCD.

Interplay between α-thalassemia and β-hemoglobinopathies: Translating genotype-phenotype relationships into therapies

α-Thalassemia represents one of the most important genetic modulators of β-hemoglobinopathies. During this last decade, the ongoing interest in characterizing genotype-phenotype relationships has yielded incredible insights into α-globin gene regulation and its impact on β-hemoglobinopathies. In this review, we provide a holistic update on α-globin gene expression stemming from DNA to RNA to protein, as well as epigenetic mechanisms that can impact gene expression and potentially influence phenotypic outcomes. Here, we highlight defined α-globin targeted strategies and rationalize the use of distinct molecular targets based on the restoration of balanced α/β-like globin chain synthesis. Considering the therapies that either increase β-globin synthesis or reactivate γ-globin gene expression, the modulation of α-globin chains as a disease modifier for β-hemoglobinopathies still remains largely uncharted in clinical studies.

Impact of hospitalized vaso-occlusive crises in the previous calendar year on mortality and complications in adults with sickle cell disease: a French population-based study

Background

Historically, sickle cell disease (SCD) patients experiencing frequent hospitalized vaso-occlusive crises (HVOC) have been associated with increased mortality, yet recent data reflecting the widespread use of hydroxyurea and advancements in disease management remain limited. Our study aims to assess the association between HVOC and mortality or severe complications in patients with SCD in this new treatment landscape.

Methods

This was a retrospective observational cohort study using the French national health data system. Between 01-01-2012 and 12-31-2018, all SCD patients ≥16 years old (ICD-10 codes D57.0-2) were included and followed until 12-31-2018. HVOC was defined as a hospitalization of ≥1 night with primary diagnosis of SCD with crisis, following an emergency room visit. The association between HVOC and severe complications was assessed with a Cox proportional hazards model.

Findings

In total, 8018 patients (56.6% females; 4538/8018) were included. The 2018 SCD standardized one-year period prevalence was 17.9 cases/100,000 person-years [17.4; 18.3]. The mean rate was 0.84 (1.88) HVOC/person-year. In 2018, 70% (5323/7605), 22% (1671/7605), and 8% (611/7605) of patients experienced 0, 1-2, or 3+ HVOCs, respectively. The median survival time between HVOCs was 415 days [386; 439]. Overall, 312 patients died (3.9%) with a mean age of 49.8 (19.4). Compared to patients without HVOC, the hazard ratios of death in patients with 1-2 or 3+ HVOCs the year prior to death were 1.67 [1.21; 2.30] and 3.70 [2.30; 5.93], respectively. Incidence of acute chest syndrome, pulmonary embolism, osteonecrosis, and sepsis increased with the HVOCs category, but not stroke. In 2018, 29.5% (180/611) of patients with 3+ HVOCs did not take hydroxyurea.

Interpretation

Patients must be closely monitored during their hospitalizations to intensify treatment and check treatment compliance. Innovative therapies are also required.

Funding

The study was funded by Novartis.

Unraveling the Complexity of Vaso-Occlusive Crises in Sickle Cell Disease: Insights from a Resource-Limited Setting

Background/Objectives: This study investigated vaso-occlusive crises (VOCs) in sickle cell disease in Lubumbashi, Democratic Republic of Congo, aiming to understand the disease complexities amidst limited resources. With sickle cell hemoglobinopathies on the rise in sub-Saharan Africa, this nine-year study explored factors associated with VOCs and hematological components. Methods: This study comprised 838 patients, analyzing VOCs and hematological changes over time. Demographic characteristics and blood composition changes were carefully categorized. A total of 2910 crises were observed and managed, with analyses conducted on severity, localization, and age groups using statistical methods. Results: The majority of crises were mild or moderate, primarily affecting osteoarticular regions. Statistical analysis revealed significant disparities in crisis intensity based on location and age. The association between blood samples and the number of comorbidities was investigated. Significant positive associations were found for all parameters, except monocytes, indicating a potential link between blood variables and complication burden. Survival analysis using Cox regression was performed to predict the probability of experiencing a second crisis. No significant effects of medication or localization were observed. However, intensity (p < 0.001), age (p < 0.001), and gender (p < 0.001) showed significant effects. Adjusted Hazard Ratios indicated increased risk with age and male gender and reduced risk with mild or severe crisis intensity compared to light. Conclusions: This research sheds light on the complexities of VOCs in resource-limited settings where sickle cell disease is prevalent. The intricate interplay between clinical, laboratory, and treatment factors is highlighted, offering insights for improved patient care. It aims to raise awareness of patient challenges and provide valuable information for targeted interventions to alleviate their burden.

Experiences and outcomes of fertility testing in male adolescents with sickle cell disease

Adult males with sickle cell disease (SCD) may have abnormal semen parameters, raising the concern that SCD and/or treatments may impact fertility. Yet, studies that include adolescents are lacking. To determine if fertility testing is feasible in male adolescents with SCD, and to explore their experiences and outcomes of fertility testing, 33 adolescents who completed a web-based SCD reproductive health education program were offered a free semen analysis. Five (15%) obtained testing and each had abnormalities. Barriers to testing included lack of time and transportation and discomfort. Findings highlight the need for larger, longitudinal studies using innovative testing approaches.

Models of care for sickle cell disease in low-income and lower-middle-income countries: a scoping review

Sickle cell disease has a growing global burden falling primarily on low-income countries (LICs) and lower-middle-income countries (LMICs) where comprehensive care is often insufficient, particularly in rural areas. Integrated care models might be beneficial for improving access to care in areas with human resource and infrastructure constraints. As part of the Centre for Integration Science's ongoing efforts to define, systematise, and implement integrated care delivery models for non-communicable diseases (NCDs), this Review explores models of care for sickle cell disease in LICs and LMICs. We identified 99 models from 136 studies, primarily done in tertiary, urban facilities in LMICs. Except for two models of integrated care for concurrent treatment of other conditions, sickle cell disease care was mostly provided in specialised clinics, which are low in number and accessibility. The scarcity of published evidence of models of care for sickle cell disease and integrated care in rural settings of LICs and LMICs shows a need to implement more integrated models to improve access, particularly in rural areas. PEN-Plus, a model of decentralised, integrated care for severe chronic non-communicable diseases, provides an approach to service integration that could fill gaps in access to comprehensive sickle cell disease care in LICs and LMICs.

Reducing transfusion utilization for children with sickle cell anemia in sub-Saharan Africa with hydroxyurea: Analysis from the phase I/II REACH trial

Children with sickle cell anemia (SCA) in Africa frequently require transfusions for SCA complications. Despite limited blood supplies, strategies to reduce their transfusion needs have not been widely evaluated or implemented. We analyzed transfusion utilization in children with SCA before and during hydroxyurea treatment. REACH (Realizing Effectiveness Across Continents with Hydroxyurea, NCT01966731) is a longitudinal Phase I/II trial of hydroxyurea in children with SCA from Angola, Democratic Republic of Congo, Kenya, and Uganda. After enrollment, children had a two-month pre-treatment screening period followed by 6 months of fixed-dose hydroxyurea (15-20 mg/kg/day), 18 months of dose escalation, and then stable dosing at maximum tolerated dose (MTD). Characteristics associated with transfusions were analyzed with univariate and multivariable models. Transfusion incidence rate ratios (IRR) across treatment periods were calculated. Among 635 enrolled children with 4124 person-years of observation, 258 participants (40.4%) received 545 transfusions. The transfusion rate per 100 person-years was 43.2 before hydroxyurea, 21.7 on fixed-dose, 14.5 during dose escalation, and 10.8 on MTD. During MTD, transfusion incidence was reduced by 75% compared to pre-treatment (IRR 0.25, 95% confidence interval [CI] 0.18-0.35, p < .0001), and by 50% compared to fixed dose (IRR 0.50, 95% CI 0.39-0.63, p < .0001). Hydroxyurea at MTD decreases transfusion utilization in African children with SCA. If widely implemented, universal testing and hydroxyurea treatment at MTD could potentially prevent 21% of all pediatric transfusions administered in sub-Saharan Africa. Increasing hydroxyurea access for SCA should decrease the transfusion burden and increase the overall blood supply.

Hydroxyurea at escalated dose versus fixed low-dose hydroxyurea in adults with sickle cell disease

Hydroxyurea reduces the frequency of vaso-occlusive complications, increases hemoglobin, and decreases mortality in sickle cell disease (SCD). Although current guidelines recommend escalation to maximum tolerated dose (MTD), the use of fixed low-dose hydroxyurea is common in low-resource countries. We conducted a systematic review and meta-analysis to evaluate the efficacy of escalated doses versus fixed low-dose of hydroxyurea in adults with SCD. Nine studies were included in the quantitative synthesis, four evaluating fixed low-dose and five evaluating escalated doses of hydroxyurea. Average daily doses of hydroxyurea in the fixed low-dose and escalated dose studies were ~10 and 22 mg/kg, respectively. There was no difference in the estimate of vaso-occlusive crisis rate between escalated and fixed low-dose studies (p = .73). The mean difference in hemoglobin from baseline to follow-up was greater for fixed low-dose than escalated dose studies (1.07 g/dL vs. 0.54 g/dL, p = .01). No difference was seen in the mean estimate of fetal hemoglobin. Despite limited eligible studies and substantial heterogeneity of effect between the studies for several outcomes, there appears to be clinical equipoise regarding the most appropriate hydroxyurea dosing regimen in adults with SCD. Controlled studies of hydroxyurea at MTD versus fixed low-dose in adults with SCD are required.

Role of hydroxyurea therapy in the prevention of organ damage in sickle cell disease: a systematic review and meta-analysis

BACKGROUND

Hydroxyurea is an affordable drug that reduces vaso-occlusive crises and transfusion requirements in sickle cell disease. However, its effectiveness in preventing chronic organ damage is still unclear. This systematic review and meta-analysis aimed to evaluate the role of hydroxyurea in preventing organ morbidity.

METHOD

We included original articles published in English from 1st January 1990 to 31st January 2023, reporting hydroxyurea therapy and organ damage from PubMed, Google Scholar, Scopus, and CrossRef databases. A total of 45 studies with 4681 sickle cell disease patients were evaluated for organ damage.

RESULTS

Our analysis showed that hydroxyurea intervention significantly lowered transcranial Doppler and tricuspid regurgitant velocity, with a standardized mean difference of - 1.03 (- 1.49; - 0.58); I 2 = 96% and - 1.37 (CI - 2.31, - 0.42); I 2 = 94%, respectively. Moreover, the pooled estimate for albuminuria showed a beneficial effect post-hydroxyurea therapy by reducing the risk of albuminuria by 58% (risk ratio of 0.42 (0.28; 0.63); I 2 = 28%).

CONCLUSION

Our study found that a hydroxyurea dose above 20 mg/kg/day with a mean rise in HbF by 18.46% post-hydroxyurea therapy had a beneficial role in reducing transcranial doppler velocity, tricuspid regurgitant velocity, albuminuria, and splenic abnormality.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023401187.

An update review of new therapies in sickle cell disease: the prospects for drug combinations

INTRODUCTION

Sickle cell disease (SCD) is an inherited disorder characterised by polymerisation of deoxygenated haemoglobin S and microvascular obstruction. The cardinal feature is generalised pain referred to as vaso-occlusive crises (VOC), multi-organ damage and premature death. SCD is the most prevalent inherited life-threatening disorders in the world and over 85% of world's 400,000 annual births occur low-and-middle-income countries. Hydroxyurea remained the only approved disease modifying therapy (1998) until the FDA approved L-glutamine (2017), Crizanlizumab and Voxelotor (2019) and gene therapies (Exa-cel and Lovo-cel, 2023).

AREAS COVERED

Clinical trials performed in the last 10 years (November 2013 - November 2023) were selected for the review. They were divided according to the mechanisms of drug action. The following pubmed central search terms [sickle cell disease] or [sickle cell anaemia] Hydroxycarbamide/ Hydroxyurea, L-Glutamine, Voxelotor, Crizanlizumab, Mitapivat, Etavopivat, gene therapy, haematopoietic stem cell transplantation, and combination therapy.

EXPERT OPINION

We recommend future trials of combination therapies for specific complications such as VOCs, chronic pain and renal impairment as well as personalised medicine approach based on phenotype and patient characteristics. Following recent approval of gene therapy for SCD, the challenge is addressing the role of shared decision-making with families, global access and affordability.

Hydroxyurea Therapy for Neurological and Cognitive Protection in Pediatric Sickle Cell Anemia in Uganda (BRAIN SAFE II): Protocol for a single-arm open label trial

Background

Children with sickle cell anemia (SCA) in Sub-Saharan Africa are at high risk of sickle cerebrovascular injury (SCVI). Hydroxyurea, a commonly used disease-modifying therapy, may prevent or decrease SCVI for reduced incident stroke, stroke risk and potentially cognitive dysfunction. We aim to test the impact of daily hydroxyurea therapy on these outcomes in Ugandan children with SCA. We hypothesize that hydroxyurea therapy over 36 months will prevent, stabilize or improve these complications of SCA.

Methods

The BRAIN SAFE II study is an open-label, single-arm trial of daily hydroxyurea for 270 children with SCA (HbSS) in Uganda, ages 3-9 years. Following baseline assessments, participants began hydroxyurea therapy and clinically followed per local guidelines. Standard hydroxyurea dose is escalated to maximum tolerated dose (MTD). SCVI is assessed by cerebral arterial velocity using Doppler ultrasound, with cognitive function determined by formal neurocognitive testing (primary outcomes). Structural SCVI is assessed by magnetic resonance imaging (MRI) and angiography (MRA) in a sub-sample of 90 participants ages ≥5 years, along with biomarkers of anemia, inflammation and malnutrition (secondary outcomes). At trial midpoint (18 months) and completion (36 months), primary outcomes will be compared to participants' baseline to determine hydroxyurea impact and relationships to secondary outcomes.

Conclusion

This open-label, single-arm trial will examine the impact of hydroxyurea on preventing or ameliorating SCA SCVI in children, assessed by reducing incident stroke, stroke risk and neurocognitive dysfunction. Trial results will provide important insight into the role of hydroxyurea therapy on critical manifestations of SCVI in children with SCA.

Predictors of Intensive Care Admission Among Adult Patients with Sickle Cell Disease in Eastern Province of Saudi Arabia

Purpose

Sickle cell disease (SCD) comprises a complex group of hematologic disorders that are collectively the most common monogenic disorder and are associated with increased risk of intensive care unit admission (ICU). The purpose of this study is to investigate factors that predict admission of adult patients with SCD to the ICU.

Patients and Methods

This was a cross-sectional study that enrolled adult patients with SCD from Saudi Arabia.

Results

A total of 107 patients with SCD, with a median age 31.9±12.1 years, were evaluated retrospectively. Regarding predictors of ICU admission, patients who indicated a history of blood transfusions were at 8.047-fold higher risk of ICU admission (OR=8.047; 95% CI=2.392-27.07; p=0.001). Patients who started hydroxyurea were at least 3.071 times more likely to be admitted than those who did not (OR=3.071; 95% CI=1.164-8.104; p=0.023). We also observed three or more hospitalizations per year to be associated with increased risk of ICU admission (OR=3.393; 95% CI=1.285-8.960; p=0.014), with those making 3 to 5 visits annually having at least 10.4 times higher risk (OR=10.38; 95% CI=10.098-98.19; p=0.041) and those with 6 to 10 ER admissions having 18 times higher risk (OR=18.00; 95% CI=2.149-150.8; p=0.008). Finally, patients with high WBC were predicted to have at least 3.34 times higher risk of ICU admission (OR=3.337; 95% CI=1.131-9.846; p=0.029).

Conclusion

SCD is a multi-systemic disease associated with increased morbidity and mortality. Recognition of high-risk features in patients helps to eliminate subjectivity in ICU referral decision. Frequent hospitalization and emergency visits, multiple blood transfusions, and elevated white blood cell count were significantly associated with a higher rate of ICU admission despite hydroxyurea usage.

Cost-Effectiveness of Hydroxyurea for Sickle Cell Anemia in a Low-Income African Setting: A Model-Based Evaluation of Two Dosing Regimens

BACKGROUND AND OBJECTIVE

The disease burden of sickle cell anemia (SCA) in sub-Saharan African (SSA) countries is substantial, with many children dying without an established diagnosis or proper treatment. The global burden of SCA is increasing each year, making therapeutic intervention a high priority. Hydroxyurea is the only disease-modifying therapy with proven feasibility and efficacy suitable for SSA; however, no one has quantified the health economic implications of its use. Therefore, from the perspective of the health care provider, we estimated the incremental cost-effectiveness of hydroxyurea as a fixed-dose regimen or maximum tolerated dose (MTD) regimen, versus SCA care without hydroxyurea.

METHODS

We estimated the cost of providing outpatient treatment at a pediatric sickle cell clinic in Kampala, Uganda. These estimates were used in a discrete-event simulation model to project mean costs (2021 US$), disability-adjusted life years (DALYs), and consumption of blood products per patient (450 mL units), for patients between 9 months and 18 years of age. We calculated cost-effectiveness as the ratio of incremental costs over incremental DALYs averted, discounted at 3% annually. To test the robustness of our findings, and the impact of uncertainty, we conducted probabilistic and one-way sensitivity analyses, scenario analysis, and price threshold analyses.

RESULTS

Hydroxyurea treatment averted an expected 1.37 DALYs and saved US$ 191 per patient if administered at the MTD, compared with SCA care without hydroxyurea. In comparison, hydroxyurea at a fixed dose averted 0.80 DALYs per patient at an incremental cost of US$ 2. The MTD strategy saved 11.2 (95% CI 11.1-11.4) units of blood per patient, compared with 9.1 (95% CI 9.0-9.2) units of blood per patient at the fixed-dose alternative.

CONCLUSIONS

Hydroxyurea at MTD is likely to improve quality of life and reduce the consumption of blood products for children with SCA living in Uganda. Compared with a fixed dose regimen, treatment dosing at MTD is likely to be a cost-effective treatment for SCA, using realistic ranges of hydroxyurea costs that are relevant across SSA. Compared with no use of the drug, hydroxyurea could lead to substantial net savings per patient, while reducing the disease morbidity and mortality and increasing quality of life.

Simultaneous adjunctive treatment of malaria and its coevolved genetic disorder sickle cell anemia

Effective treatments for genetic disorders that coevolved with pathogens require simultaneous betterment of both conditions. Hydroxyurea (HU) offers safe and efficacious treatment for sickle cell anemia (SCA) by reducing clinical complications, transfusions, and death rates. Despite concerns that the HU treatment for SCA would increase infection risk by the human malaria Plasmodium falciparum, (the genetic driver of the sickle mutation), HU instead reduced clinical malaria. We used physiologically relevant drug exposures that mimic in vivo pharmacokinetics in humans. Under these conditions, we showed that HU and other ribonucleotide reductase (RNR) inhibitors have significant, intrinsic killing activity in vitro against schizont stages of P falciparum in both normal and sickle red blood cells. Long-term in vitro selection with HU increased the expression of Pfrnr genes but showed a low risk of eliciting stably resistant parasites or compromising the potency of current antimalarial drugs. Additive activity devoid of antagonism by HU was observed with a wide spectrum of commonly used antimalarial treatments. These data endorse broad, safe, and long-term use of HU for SCA in malaria-endemic countries and provide a novel biological model for the treatment of a genetic disorder with simultaneous, adjunct therapy of a life-threatening infection needed in a global health setting.

Hydroxyurea does not reverse functional alterations of the nitric oxide-cGMP pathway associated with priapism phenotype in corpus cavernosum from sickle cell mouse

Sickle cell disease (SCD) is a genetic disorder that has been associated with priapism. The role of hydroxyurea, a common SCD therapy, in influencing the nitric oxide (NO)-cGMP pathway and its effect on priapism is unclear. To investigate the effect of hydroxyurea treatment on smooth muscle relaxation of corpus cavernosum induced by stimulation of the NO-cGMP pathway in SCD transgenic mice and endothelial NO synthase gene-deficient (eNOS-/-) mice, which are used as model of priapism associated with the low bioavailability of endothelial NO. Four-month-old wild-type (WT, C57BL/6), SCD transgenic, and eNOS-/- male mice were treated with hydroxyurea (100 mg/Kg/day) or its vehicle (saline) daily for three weeks via intraperitoneal injections. Concentration-response curves for acetylcholine (ACh), sodium nitroprusside (SNP), and electrical field stimulation (EFS) were generated using strips of mice corpus cavernosum. The SCD mice demonstrated an amplified CC relaxation response triggered by ACh, EFS, and SNP. The corpus cavernosum relaxation responses to SNP and EFS were found to be heightened in the eNOS-/- group. However, the hydroxyurea treatment did not alter these escalated relaxation responses to ACh, EFS, and SNP in the corpus cavernosum of the SCD group, nor the relaxation responses to EFS and SNP in the eNOS-/- group. In conclusion, hydroxyurea is not effective in treating priapism associated with SCD. It is likely that excess plasma hemoglobin and reactive oxygen species, which are reported in SCD, are reacting with NO before it binds to GCs in the smooth muscle of the corpus cavernosum, thus preventing the restoration of baseline NO/cGMP levels. Furthermore, the downregulation of eNOS in the penis may impair the pharmacological action of hydroxyurea at the endothelial level in SCD mice. This study emphasize the urgency for exploring alternative therapeutic avenues for priapism in SCD that are not hindered by high plasma hemoglobin and ROS levels.

F-erythrocytes promote Plasmodium falciparum proliferation in sickle cell disease

BACKGROUND

Sickle cell disease (SCD) remains prevalent because heterozygous carriers (HbAS) are partially resistant to Plasmodium falciparum malaria. Sickle hemoglobin (HbS) polymerization in low and intermediate oxygen (O2 ) conditions is the main driver of HbAS-driven resistance to P. falciparum malaria. However, epidemiological studies have reported mixed malaria morbidity and mortality outcomes in individuals with sickle cell disease (SCD). While maximum-tolerated dose hydroxyurea has been shown to lower malaria incidence, fetal hemoglobin (HbF), an inhibitor of HbS polymerization that is variably packaged in F-erythrocytes, might provide hemoglobin that is accessible to the parasite for feeding.

METHODS

To explore that risk, we examined the effect of variable mean corpuscular fetal hemoglobin (MCHF) on P. falciparum proliferation, invasion, and development in HbSS RBCs.

RESULTS

We found that greater MCHF in HbSS red blood cells (RBCs) is associated with increased P. falciparum proliferation in O2 environments comparable with the microcirculation. Moreover, both parasite invasion and intracellular growth, the major components of proliferation, occur predominantly in F-erythrocytes and are augmented with increasing MCHF.

CONCLUSIONS

HbF modifies P. falciparum infection in HbSS RBCs, further highlighting the complexity of the molecular interactions between these two diseases. Other inhibitors of HbS polymerization that do not increase HbF or F-erythrocytes should be independently assessed for their effects on P. falciparum malaria proliferation in HbSS RBCs.

Prospective identification of variables as outcomes for treatment (PIVOT): study protocol for a randomised, placebo-controlled trial of hydroxyurea for Ghanaian children and adults with haemoglobin SC disease

BACKGROUND

Haemoglobin SC (HbSC) is a common form of sickle cell disease (SCD), especially among individuals of West African ancestry. Persons with HbSC disease suffer from the same clinical complications and reduced quality of life that affect those with sickle cell anaemia (HbSS/Sβ0). Retrospective anecdotal data suggest short-term safety and benefits of hydroxyurea for treating HbSC, yet rigorous prospective data are lacking regarding optimal dosing, clinical and laboratory effects, long-term safety and benefits, and appropriate endpoints to monitor. Prospective Investigation of Variables as Outcomes for Treatment (PIVOT) was designed with three aims: (1) to measure the toxicities of hydroxyurea treatment on laboratory parameters, (2) to assess the effects of hydroxyurea treatment on sickle-related clinical and laboratory parameters, and (3) to identify study endpoints suitable for a future definitive phase III trial of hydroxyurea treatment of HbSC disease.

METHODS

PIVOT is a randomised, placebo-controlled, double blind clinical trial of hydroxyurea. Approximately 120 children and 120 adults ages 5-50 years with HbSC disease will be enrolled, screened for 2 months, and then randomised 1:1 to once-daily oral hydroxyurea or placebo. Study treatment will be prescribed initially at 20 ± 5 mg/kg/day with an opportunity to escalate the dose twice over the first 6 months. After 12 months of blinded study treatment, all participants will be offered open-label hydroxyurea for up to 4 years. Safety outcomes include treatment-related cytopenias, whole blood viscosity, and adverse events. Efficacy outcomes include a variety of laboratory and clinical parameters over the first 12 months of randomised treatment, including changes in haemoglobin and fetal haemoglobin, intracranial arterial velocities measured by transcranial Doppler ultrasound, cerebral oxygenation using near infrared spectrometry, spleen volume and kidney size by ultrasound, proteinuria, and retinal imaging. Exploratory outcomes include functional erythrocyte analyses with ektacytometry for red blood cell deformability and point-of-sickling, patient-reported outcomes using the PROMIS questionnaire, and 6-min walk test.

DISCUSSION

For children and adults with HbSC disease, PIVOT will determine the safety of hydroxyurea and identify measurable changes in laboratory and clinical parameters, suitable for future prospective testing in a definitive multi-centre phase III clinical trial.

TRIAL REGISTRATION

PACTR, PACTR202108893981080. Registered 24 August 2021, https://pactr.samrc.ac.za.

Genetic reversal of the globin switch concurrently modulates both fetal and sickle hemoglobin and reduces red cell sickling

We previously reported initial clinical results of post-transcriptional gene silencing of BCL11A expression (NCT03282656) reversing the fetal to adult hemoglobin switch. A goal of this approach is to increase fetal hemoglobin (HbF) expression while coordinately reducing sickle hemoglobin (HbS) expression. The resulting combinatorial effect should prove effective in inhibiting HbS polymerization at lower physiologic oxygen values thereby mitigating disease complications. Here we report results of exploratory single-cell analysis of patients in which BCL11A is targeted molecularly and compare results with cells of patients treated with hydroxyurea (HU), the current standard of care. We use single-cell assays to assess HbF, HbS, oxygen saturation, and hemoglobin polymer content in RBCs for nine gene therapy trial subjects (BCLshmiR, median HbF% = 27.9) and compare them to 10 HU-treated subjects demonstrating high and comparable levels of HbF (HU High Responders, median HbF% = 27.0). All BCL11A patients achieved the primary endpoint for NCT03282656, which was defined by an absolute neutrophil count greater than or equal to 0.5 × 109 cells/L for three consecutive days, achieved within 7 weeks following infusion. Flow cytometric assessment of single-RBC HbF and HbS shows fewer RBCs with high HbS% that would be most susceptible to sickling in BCLshmiR vs. HU High Responders: median 42% of RBCs with HbS%>70% in BCLshmiR vs. 61% in HU High Responders (p = 0.004). BCLshmiR subjects also demonstrate more RBCs resistant to HbS polymerization at lower physiologic oxygen tension: median 32% vs. 25% in HU High Responders (p = 0.006). Gene therapy-induced BCL11A down-regulation reverses the fetal-to-adult hemoglobin switch and induces RBCs with higher HbF%, lower HbS%, and greater resistance to deoxygenation-induced polymerization in clinical trial subjects compared with a cohort of highly responsive hydroxyurea-treated subjects.

Access to essential therapy for sickle cell disease in Africa: Experience from a national program in Ghana

Novartis, a global medicines company, and the Sickle Cell Foundation of Ghana (SCFG), an advocacy organization, have endeavored to support the implementation of global best practices in the care of people living with sickle cell disease (SCD) in Africa, and to address unmet needs relating to this condition on the continent. Beginning in 2019, a multifaceted SCD program was implemented in Ghana through a public-private partnership involving the government of Ghana, the SCFG, Novartis, and other partners. A key component of the program involved expanding the reach of hydroxyurea (HU), the only approved disease-modifying generic treatment for SCD, in ways that would promote sustainable access. The program helped to raise the profile of SCD in Ghana and, in 2022, the government adopted HU into its National Health Insurance Scheme. Features of the effort in Ghana are now being expanded to other countries in Africa through cocreated programs with in-country partners. This article reviews the program's history, progress, challenges, and lessons learned.

Therapeutic perspective for children and young adults living with thalassemia and sickle cell disease

Hemoglobinopathies, including thalassemias and sickle cell disease, are the most common monogenic diseases worldwide, with estimated annual births of more than 330,000 affected infants. Hemoglobin disorders account for about 3.4% of deaths in children under 5 years of age. The distribution of these diseases is historically linked to current or previously malaria-endemic regions; however, immigration has led to a worldwide distribution of these diseases, making them a global health problem. During the last decade, new treatment approaches and novel therapies have been proposed, some of which have the potential to change the natural history of these disorders. Indeed, the first erythroid maturation agent, luspatercept, and gene therapy have been approved for beta-thalassemia adult patients. For sickle cell disease, molecules targeting vaso-occlusion and hemoglobin S polymerization include crizanlizumab, which has been approved for patients ≥ 16 years, voxelotor approved for patients ≥ 12 years, and L-glutamine for patients older than 5 years.    Conclusion: We herein present the most recent advances and future perspectives in thalassemia and sickle cell disease treatment, including new drugs, gene therapy, and gene editing, and the current clinical trial status in the pediatric populations. What is Known: • Red blood cell transfusions, iron chelation therapy and hematopoietic stem cell transplantation have been the mainstay of treatment of thalassemia patients for decades. • For sickle cell disease, until 2005, treatment strategies were mostly the same as those for thalassemia, with the option of simple transfusion or exchange transfusion. In 2007, hydroxyurea was approved for patients ≥ 2 years old. What is New: • In 2019, gene therapy with betibeglogene autotemcel (LentiGlobin BB305) was approved for TDT patients ≥ 12 years old non β0/β0 without matched sibling donor. • Starting from 2017 several new drugs, such as L-glutamine (approved only by FDA), crizanlizumab (approved by FDA and EMA for patients ≥ 16 years), and lastly voxelotor (approved by FDA and EMA for patients ≥ 12 years old).

Hydroxyurea pharmacokinetics and precision dosing in low-resource settings

Introduction: Hydroxyurea is effective disease-modifying treatment for sickle cell anemia (SCA). Escalation to maximum tolerated dose (MTD) achieves superior benefits without additional toxicities, but requires dose adjustments with serial monitoring. Pharmacokinetic (PK)-guided dosing can predict a personalized optimal dose, which approximates MTD and requires fewer clinical visits, laboratory assessments, and dose adjustments. However, PK-guided dosing requires complex analytical techniques unavailable in low-resource settings. Simplified hydroxyurea PK analysis could optimize dosing and increase access to treatment. Methods: Concentrated stock solutions of reagents for chemical detection of serum hydroxyurea using HPLC were prepared and stored at -80C. On the day of analysis, hydroxyurea was serially diluted in human serum, then spiked with N-methylurea as an internal standard and analyzed using two commercial HPLC machines: 1) standard benchtop Agilent with 449 nm detector and 5 micron C18 column; and 2) portable PolyLC with 415 nm detector and 3.5 micron C18 column. After validation in the United States, the portable HPLC and chemicals were transported to Tanzania. Results: A calibration curve using hydroxyurea 2-fold dilutions ranging from 0 to 1000 µM was plotted against the hydroxyurea:N-methylurea ratio. In the United States, both HPLC systems yielded calibration curves with R² > 0.99. Hydroxyurea prepared at known concentrations confirmed accuracy and precision within 10%-20% of the actual values. Both HPLC systems measured hydroxyurea with <10% variance from the prepared concentrations, and paired analysis of samples on both machines documented <15% variance. Serial measurements of 300 and 100 μM concentrations using the PolyLC system were precise with 2.5% coefficient of variance. After transport to Tanzania with setup and training, the modified PolyLC HPLC system produced similar calibration curves with R² > 0.99. Conclusion: Increasing access to hydroxyurea for people with SCA requires an approach that eases financial and logistical barriers while optimizing safety and benefits, especially in low-resource settings. We successfully modified a portable HPLC instrument to quantify hydroxyurea, validated its precision and accuracy, and confirmed capacity building and knowledge transfer to Tanzania. HPLC measurement of serum hydroxyurea is now feasible in low-resource settings using available laboratory infrastructure. PK-guided dosing of hydroxyurea will be tested prospectively to achieve optimal treatment responses.

Hydroxyurea with dose escalation for primary stroke risk reduction in children with sickle cell anaemia in Tanzania (SPHERE): an open-label, phase 2 trial

BACKGROUND

Transcranial Doppler screening with chronic transfusions reduces stroke risk in children with sickle cell anaemia but is not feasible in low-resource settings. Hydroxyurea is an alternative treatment to decrease stroke risk. We aimed to estimate stroke risk in children with sickle cell anaemia in Tanzania and to determine the efficacy of hydroxyurea to decrease and prevent stroke.

METHODS

We did an open-label, phase 2 trial (SPHERE) at Bugando Medical Centre, Mwanza, Tanzania. Children aged 2-16 years with a diagnosis of sickle cell anaemia confirmed by haemoglobin electrophoresis were eligible for enrolment. Participants had transcranial Doppler ultrasound screening by a local examiner. Participants with elevated Doppler velocities, either conditional (170-199 cm/s) or abnormal (≥200 cm/s), received oral hydroxyurea starting at 20 mg/kg once daily and escalated every 8 weeks by 5 mg/kg per day to the maximum tolerated dose. Participants with normal Doppler velocities (<170 cm/s) received usual care from the sickle cell anaemia clinic and were rescreened after 12 months to determine whether they qualified for treatment on trial. The primary endpoint was change in transcranial Doppler velocity from the baseline visit to after 12 months of hydroxyurea treatment, analysed in all patients who had paired baseline and follow-up measurements collected after 12 months of treatment. Safety was analysed in the per-protocol population (all participants who received study treatment). This study is registered with ClinicalTrials.gov, NCT03948867.

FINDINGS

Between April 24, 2019, and April 9, 2020, 202 children were enrolled and had transcranial Doppler screening. Sickle cell anaemia was confirmed by DNA-based testing in 196 participants (mean age 6·8 years [SD 3·5], 103 [53%] were female, and 93 [47%] were male). At the baseline screening, 47 (24%) of 196 participants had elevated transcranial Doppler velocities (43 [22%] conditional, four [2%] abnormal); 45 initiated hydroxyurea at a mean dose of 20·2 mg/kg per day (SD 1·4) with escalation to a mean dose of 27·4 mg/kg per day (5·1) after 12 months. Treatment response was analysed after 12 months (± 1 month; median 11 months, IQR 11-12) and 24 months (±3 months; median 22 months, 22-22). Transcranial Doppler velocities decreased to a mean of 149 cm/s (SD 27) compared with 182 cm/s (12) at baseline, which was significantly lower than baseline (p<0·0001), with an average decline of 35 cm/s (SD 23) after 12 months of treatment in 42 participants with paired results available at baseline and 12 months. No clinical strokes occurred, and 35 (83%) of 42 participants reverted to normal transcranial Doppler velocities. Clinical adverse events were mild, and dose-limiting toxicities were uncommon. The most common grade 3 adverse events were malaria (12 [29%] episodes in 45 patients) and sepsis (13 [32%] episodes). There were three serious adverse events, none of which were treatment-related, and no treatment-related deaths occurred.

INTERPRETATION

Children with sickle cell anaemia in Tanzania have a high baseline stroke risk. Hydroxyurea at the maximum tolerated dose significantly lowers transcranial Doppler velocities and reduces primary stroke risk. Transcranial Doppler screening plus hydroxyurea at the maximum tolerated dose is an effective stroke prevention strategy, supporting wider hydroxyurea access for patients with sickle cell anaemia across sub-Saharan Africa.

FUNDING

American Society of Hematology, National Institutes of Health, Cincinnati Children's Research Foundation.

Efficacy and safety of pharmacological interventions for managing sickle cell disease complications in children and adolescents: Systematic review with network meta-analysis

This study aimed to synthesize the evidence on the effects of disease-modifying agents for managing sickle cell disease (SCD) in children and adolescents by means of a systematic review with network meta-analyses, surface under the cumulative ranking curve (SUCRA) and stochastic multicriteria acceptability analyses (SMAA) (CRD42022328471). Eightteen randomized controlled trials (hydroxyurea [n = 7], l-arginine [n = 3], antiplatelets [n = 2], immunotherapy/monoclonal antibodies [n = 2], sulfates [n = 2], docosahexaenoic acid [n = 1], niprisan [n = 1]) were analyzed. SUCRA and SMAA demonstrated that hydroxyurea at higher doses (30 mg/kg/day) or at fixed doses (20 mg/kg/day) and immunotherapy/monoclonal antibodies are more effective for preventing vaso-occlusive crisis (i.e., lower probabilities of incidence of this event; 14, 25, and 30%, respectively), acute chest syndrome (probabilities ranging from 8 to 30%), and needing of transfusions (11-31%), while l-arginine (100-200 mg/kg) and placebo were more prone to these events. Therapies were overall considered safe; however, antiplatelets and sulfates may lead to more severe adverse events. Although the evidence was graded as insufficient and weak, hydroxyurea remains the standard of care for this population, especially if a maximum tolerated dose schedule is considered.

Quantitative MRI evaluation of bone marrow in sickle cell disease: relationship with haemolysis and clinical severity

AIM

To evaluate bone marrow fat fraction using the Dixon technique (FFDix) of magnetic resonance imaging (MRI) as a potential biomarker of haemolysis and clinical severity in the overall assessment and follow-up of sickle cell disease (SCD) patients.

MATERIAL AND METHODS

The present study was a cross-sectional study in which healthy individuals and SCD patients (matched for age, sex, and weight) were subjected to MRI of the lumbar spine and pelvis to quantify FFDix in the bone marrow using the Dixon technique. SCD severity was analysed by clinical and laboratory data, and an online calculator. A high degree of haemolysis was defined using the cut-off values haemoglobin (Hb) ≤10 g/dl, lactate dehydrogenase (LDH) ≥325 U/l, reticulocytes ≥3% and total bilirubin (TB) ≥1.2 mg/dl. Pearson's correlation, receiver operating characteristic (ROC) curve and binary logistic regression analysis were performed.

RESULTS

Forty-eight SCD patients (26 homozygous: HbSS and 22 compound heterozygous: HbSC) and 48 healthy individuals participated in the study. FFDix was lower in SCD patients than in the control group, showing even lower values in the HbSS subtype and patients with a higher degree of haemolysis. HbSC patients with a higher degree of haemolysis using hydroxyurea (medium dosage 9.8 mg/kg/day) had lower FFDix. ROC curves and odds ratios for detecting patients with a higher degree of haemolysis at the different FFDix measurement sites demonstrated excellent performance: iliac bones (cut-off ≤16.75%, AUC = 0.824, p<0.001), femoral heads (cut-off ≤46.7%, AUC = 0.775, p=0.001), lumbar vertebrae (cut-off ≤7.8%, AUC = 0.755, p=0.002).

CONCLUSION

Decreased FFDix is indicative of higher degree of haemolysis and SCD severity with great potential as a non-invasive biomarker contributing to the overall assessment and follow-up of SCD patients.

Design of an adaptive randomized clinical trial of intravenous citrulline for sickle cell pain crisis in the emergency department

Background

Vaso-occlusive pain crisis (VOC) is the most frequent cause for Emergency Department (ED) visits and hospital admissions for patients with sickle cell disease (SCD). Nitric oxide plays a critical role in the pathogenesis of vaso-occlusion. The amino acid, citrulline, is the main endothelial nitric oxide booster that offers the potential to ameliorate vaso-occlusion and decrease the risk of hospitalization.

Objective

In this two-part study, the goal of the first part is to determine the pharmacokinetic profile of intravenous (IV) l-citrulline and optimal dose for the second part of the study, which is to determine the efficacy and tolerability of the intervention in patients with SCD.

Design

A phase I/IIA open-label dose-finding study with subsequent double-blind, placebo-controlled, randomized Study of l-citrulline in children and adolescents with SCD presenting to the ED in VOC.

Methods

Part 1: Subjects experiencing VOC are enrolled in an open-label, ascending dose of IV l-citrulline to identify the optimum dose with endpoints of pharmacokinetic parameters, pain scores, reduction of opioid use, quality of life, proportion admitted to the hospital for treatment of pain, readmission rates, and assessment of adverse events. Part 2 of the trial is a double-blind, placebo-controlled adaptive "pick-the-winner" design to evaluate the efficacy and tolerability of IV l-citrulline in patients with SCD while receiving standard of care therapy for VOC.

Summary

This ED based sickle cell adaptive trial will determine the optimal dose for IV citrulline and whether the intervention improves outcome as a potential novel therapy for VOC in SCD.

Introduction of Hydroxyurea Therapy to a Cohort of Sickle Cell Patients in Northern Haiti

Although the prevalence of sickle cell anemia is high in Haiti, treatment with hydroxyurea (HU) is uncommon. HU therapy was started at a hospital in Northern Haiti for children and young adults who had presented with complications of their disease. The patients were followed in clinic for their response to therapy and the principal outcome was hospitalization for complications. There was a 70% decrease in the rate of hospitalization in the cohort with no significant complications or deaths during the study period. Treatment with HU is a proven therapy that reduces the morbidity associated with sickle cell anemia and efforts should be made to assure access and affordability in regions with a high prevalence.

Hydroxyurea (hydroxycarbamide) for sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is one of the most common inherited diseases worldwide. It is associated with lifelong morbidity and a reduced life expectancy. Hydroxyurea (hydroxycarbamide), an oral chemotherapeutic drug, ameliorates some of the clinical problems of SCD, in particular that of pain, by raising foetal haemoglobin (HbF). This is an update of a previously published Cochrane Review.

OBJECTIVES

The aims of this review are to determine through a review of randomised or quasi-randomised studies whether the use of hydroxyurea in people with SCD alters the pattern of acute events, including pain; prevents, delays or reverses organ dysfunction; alters mortality and quality of life; or is associated with adverse effects. In addition, we hoped to assess whether the response to hydroxyurea in SCD varies with the type of SCD, age of the individual, duration and dose of treatment, and healthcare setting.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Haemoglobinopathies Register, comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. We also searched online trial registries. The date of the most recent search was 17 February 2022.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials (RCTs and quasi-RCTs), of one month or longer, comparing hydroxyurea with placebo or standard therapy in people  with SCD.

DATA COLLECTION AND ANALYSIS

Authors independently assessed studies for inclusion, carried out data extraction, assessed the risk of bias and assessed the quality of the evidence using GRADE.

MAIN RESULTS

We included nine RCTs recruiting 1104 adults and children with SCD (haemoglobin SS (HbSS), haemoglobin SC (HbSC) or haemoglobin Sβºthalassaemia (HbSβºthal) genotypes). Studies lasted from six to 30 months. We judged the quality of the evidence for the first two comparisons below as moderate to low as the studies contributing to these comparisons were mostly large and well-designed (and at low risk of bias); however, the evidence was limited and imprecise for some outcomes such as quality of life, deaths during the studies and adverse events, and the results are applicable only to individuals with HbSS and HbSβºthal genotypes. We judged the quality of the evidence for the third and fourth comparisons to be very low due to the limited number of participants, the lack of statistical power (both studies were terminated early with approximately only 20% of their target sample size recruited) and the lack of applicability to all age groups and genotypes. Hydroxyurea versus placebo Five studies (784 adults and children with HbSS or HbSβºthal) compared hydroxyurea to placebo; four recruited individuals with only severe disease and one recruited individuals with all disease severities. Hydroxyurea probably improves pain alteration (using measures such as pain crisis frequency, duration, intensity, hospital admissions and opoid use) and life-threatening illness, but we found no difference in death rates (10 deaths occurred during the studies, but the rates did not differ by treatment group) (all moderate-quality evidence). Hydroxyurea may improve measures of HbF (low-quality evidence) and probably decreases neutrophil counts (moderate-quality evidence). There were no consistent differences in terms of quality of life and adverse events (including serious or life-threatening events) (low-quality evidence). There were fewer occurrences of acute chest syndrome and blood transfusions in the hydroxyurea groups.  Hydroxyurea and phlebotomy versus transfusion and chelation Two studies (254 children with HbSS or HbSβºthal also with risk of primary or secondary stroke) contributed to this comparison. There were no consistent differences in terms of pain alteration, death or adverse events (low-quality evidence) or life-threatening illness (moderate-quality evidence). Hydroxyurea with phlebotomy probably increased HbF and decreased neutrophil counts (moderate-quality evidence), but there were more occurrences of acute chest syndrome and infections. Quality of life was not reported. In the primary prevention study, no strokes occurred in either treatment group but in the secondary prevention study, seven strokes occurred in the hydroxyurea and phlebotomy group (none in the transfusion and chelation group) and the study was terminated early.  Hydroxyurea versus observation One study (22 children with HbSS or HbSβºthal also at risk of stoke) compared hydroxyurea to observation. Pain alteration and quality of life were not reported. There were no differences in life-threatening illness, death (no deaths reported in either group) or adverse events (very low-quality evidence). We are uncertain if hydroxyurea improves HbF or decreases neutrophil counts (very low-quality evidence). Treatment regimens with and without hydroxyurea One study (44 adults and children with HbSC) compared treatment regimens with and without hydroxyurea. Pain alteration, life-threatening illness and quality of life were not reported. There were no differences in death rates (no deaths reported in either group), adverse events or neutrophil levels (very low-quality evidence). We are uncertain if hydroxyurea improves HbF (very low-quality evidence).

AUTHORS' CONCLUSIONS

There is evidence to suggest that hydroxyurea may be effective in decreasing the frequency of pain episodes and other acute complications in adults and children with sickle cell anaemia of HbSS or HbSβºthal genotypes and in preventing life-threatening neurological events in those with sickle cell anaemia at risk of primary stroke by maintaining transcranial Doppler velocities. However, there is still insufficient evidence on the long-term benefits of hydroxyurea, particularly with regard to preventing chronic complications of SCD, or recommending a standard dose or dose escalation to maximum tolerated dose. There is also insufficient evidence about the long-term risks of hydroxyurea, including its effects on fertility and reproduction. Evidence is also limited on the effects of hydroxyurea on individuals with the HbSC genotype. Future studies should be designed to address such uncertainties.

Precision Medicine and Sickle Cell Disease

Sickle cell disease (SCD) is characterized by variable clinical outcomes, with some patients suffering life-threatening complications during childhood, and others living relatively symptom-free into old age. Because of this variability, there is an important potential role for precision medicine, in which particular different treatments are selected for different groups of patients. However, the application of precision medicine in SCD is limited by difficulties in identifying different prognostic groups and the small number of available treatments. The main genetic determinant of outcomes in SCD is the underlying β-globin genotype, with sickle cell anemia (HbSS) and hemoglobin SC disease (HbSC) forming the 2 major forms of the disease in most populations of African origin. Although there are clear differences in clinical outcomes between these conditions, treatments approaches are very similar, with little evidence on how to treat HbSC in particular. Other genomic information, such as the co-inheritance of α-thalassemia, or high fetal hemoglobin (HbF) levels, is of some prognostic value but insufficient to determine treatments. Precision medicine is further limited by the fact that the 2 main drugs used in SCD, penicillin and hydroxyurea, are currently recommended for all patients. Newer treatments, such as crizanlizumab and voxelotor, raise the possibility that groups will emerge who respond best to particular drugs or combinations. Perhaps the best current example of precision medicine in SCD is the selective use of blood transfusions as primary stroke prevention in children with evidence of cerebral vasculopathy. More precise treatments may emerge as we understand more about the pathology of SCD, including problems with erythropoiesis.

Stroke Prevention with Hydroxyurea Enabled through Research and Education: A Phase 2 Primary Stroke Prevention Trial in Sub-Saharan Africa

INTRODUCTION

Stroke is a severe complication of sickle cell anemia (SCA), with devastating sequelae. Transcranial Doppler (TCD) ultrasonography predicts stroke risk, but implementing TCD screening with suitable treatment for primary stroke prevention in low-resource environments remains challenging. SPHERE (NCT03948867) is a prospective phase 2 open-label hydroxyurea trial for SCA in Tanzania.

METHODS

After formal training and certification, local personnel screened children 2-16 years old; those with conditional (170-199 cm/s) or abnormal (≥200 cm/s) time-averaged mean velocities (TAMVs) received hydroxyurea at 20 mg/kg/day with dose escalation to maximum tolerated dose (MTD). The primary study endpoint is change in TAMV after 12 months of hydroxyurea; secondary endpoints include SCA-related clinical events, splenic volume and function, renal function, infections, hydroxyurea pharmacokinetics, and genetic modifiers.

RESULTS

Between April 2019 and April 2020, 202 children (average 6.8 ± 3.5 years, 53% female) enrolled and underwent TCD screening; 196 were deemed eligible by DNA testing. Most had numerous previous hospitalizations and transfusions, with low baseline hemoglobin (7.7 ± 1.1 g/dL) and %HbF (9.3 ± 5.4%). Palpable splenomegaly was present at enrollment in 49 (25%); average sonographic splenic volume was 103 mL (range 8-1,045 mL). TCD screening identified 22% conditional and 2% abnormal velocities, with hydroxyurea treatment initiated in 96% (45/47) eligible children.

CONCLUSION

SPHERE has built local capacity with high-quality research infrastructure and TCD screening for SCA in Tanzania. Fully enrolled participants have a high prevalence of elevated baseline TCD velocities and splenomegaly. SPHERE will prospectively determine the benefits of hydroxyurea at MTD for primary stroke prevention, anticipating expanded access to hydroxyurea treatment across Tanzania.

Determinants of severity in sickle cell disease

Sickle cell disease is a very variable condition, with outcomes ranging from death in childhood to living relatively symptom free into the 8^th decade. Much of this variability is unexplained. The co-inheritance of α thalassaemia and factors determining HbF levels significantly modify the phenotype, but few other significant genetic variants have been identified, despite extensive studies. Environmental factors are undoubtedly important, with socio-economics and access to basic medical care explaining the huge differences in outcomes between many low- and high-income countries. Exposure to cold and windy weather seems to precipitate acute complications in many people, although these effects are unpredictable and vary with geography. Many studies have tried to identify prognostic factors which can be used to predict outcomes, particularly when applied in infancy. Overall, low haemoglobin, low haemoglobin F percentage and high reticulocytes in childhood are associated with worse outcomes, although again these effects are fairly weak and inconsistent.

Impact of hydroxyurea dose and adherence on hematologic outcomes for children with sickle cell anemia

BACKGROUND

Hydroxyurea is the primary treatment for sickle cell anemia (SCA), yet real-world implementation in high-income settings is suboptimal. Variation in prescribed hydroxyurea dose and patient adherence in these settings can both affect actual exposure to hydroxyurea. Quantifying the contributions of hydroxyurea dose and medication adherence to the relationship between hydroxyurea exposure and hematologic parameters could inform strategies to optimize exposure and improve outcomes.

PROCEDURE

We evaluated the relationship between hydroxyurea exposure, defined by average prescribed dose and adherence, and hematologic parameters using data from children with SCA who were enrolled in two prospective hydroxyurea adherence studies. Hydroxyurea adherence was assessed by video directly observed therapy or electronic pill bottle and medication administration record. Average prescribed dose was abstracted from prescriptions in patients' electronic medical record. Participants with a hydroxyurea exposure >20 mg/kg/day and ≤20 mg/kg/day were included in the higher and lower exposure groups, respectively.

RESULTS

Forty-five participants were included in the analysis (56% male; median age 12 years [range 2-19]; 98% Black). Higher exposed participants (n = 23) were prescribed a higher dose (27.2 vs. 24.4 mg/kg/day, p = .002) and had better adherence (0.92 vs. 0.71, p ≤ .001) compared to lower exposed participants (n = 22). Higher exposure was associated with higher fetal hemoglobin (p = .04) and mean corpuscular volume (p = .02).

CONCLUSIONS

Higher hydroxyurea exposure is associated with improved hematologic parameters in the high-income setting and is affected by both prescribed dose and adherence. Future studies are needed to optimize both adherence and hydroxyurea prescribing and confirm that increasing exposure improves clinical outcomes in this setting.

Strategies to increase access to basic sickle cell disease care in low- and middle-income countries

INTRODUCTION

Sickle cell disease (SCD) is the most common hemoglobinopathy in the world. Over 90% of those born with SCD live in low- and middle-income countries (LMICs), yet individuals in these settings have much poorer outcomes compared to those in high-income countries.

AREAS COVERED

This manuscript provides an in-depth review of the cornerstones of basic SCD care, the barriers to implementing these in LMICs, and strategies to increase access in these regions. Publications in English language, peer-reviewed, and edited from 2000 to 2021 were identified on PubMed. Google search was used for gray literature.

EXPERT OPINION

Outcomes for patients with SCD in high-income countries have improved over the last few decades due to the implementation of universal newborn screening programs and use of routine antimicrobial prophylaxis, increase in therapeutic and curative options, and the adoption of specific measures to decrease risk of stroke. This success has not translated to LMICs due to several reasons including resource constraints. A combination of several strategies is needed to increase access to basic SCD care for patients in these settings.

Diminished ovarian reserve in young women with sickle cell anemia

Women with sickle cell anemia (SCA) have higher rates of diminished ovarian reserve (DOR) than age-matched controls. Pecker et al report a small study of patients with SCA that compares ovarian reserve in patients after stem cell transplant, on therapy with hydroxyurea (HU), and on supportive care. As expected, patients who received transplants have severe DOR. About one-third of patients on HU have DOR, while DOR was absent in patients on supportive care. Whether this reflects an impact of HU or is a biomarker of severe disease remains to be established in a larger study.

Pediatric Sickle Cell Disease in Sudan: Complications and Management

Background. Sickle cell disease (SCD) is a life-threatening genetic disorder due to the formation of sickle hemoglobin molecule (HbS) that polymerizes in hypoxic conditions leading to SCD-related complications. Different approaches have been used in the management of SCD including symptomatic management, supportive management, and preventive management. Objectives. To assess the management of SCD in pediatric patients in Gaafar Ibnauf Referral Hospital in Khartoum locality, Sudan. Method. A descriptive, retrospective, hospital-based study was conducted in Gaafar Ibnauf Hospital using a data collection sheet. The study included all medical files of pediatric patients with SCD attending the hospital during the period from the first of April 2018 to the first of July 2018. The data were analyzed using descriptive statistics and the chi-square test. $P<0.05$ was considered statistically significant. Results. Out of 207 pediatric patients, 53.1% were females (mean age of 7.5 ± 3.1 years), with a 1.1 : 1 female:male ratio and low socioeconomic status. Only 4.3% of participants had health insurance. The Messeryia tribe in western Sudan had the highest prevalence of the disease among the Sudanese tribes (11.1%). Vaso-occlusive crisis (33.3%), infections (13.5%), and neurological complications (10.6%) were the most frequent complications reported during routine visits. After initiation of management, only 3.4% of pediatric patients had hemolytic crises, and 1.4% of the anemic patients had splenomegaly. 100% of patients received folic acid, 73.9% used hydroxyurea, and 69.6% underwent blood transfusion for the management of SCD. Prophylactic penicillin was prescribed for 15% of patients, and 41.1% were immunized with pneumococcal vaccine (PPSV23). Most patients had been scheduled for planned follow-up visits every 3–6 months (93.2%). Hydroxyurea and blood transfusion significantly reduced fever and vaso-occlusive crisis. Conclusion. The SCD treatment protocol in Gaafar Ibnauf Children’s Hospital, involving preventive and symptomatic therapy, is consistent with the internationally implemented protocols for SCD management. However, immunization and prophylactic penicillin approaches are deficient.

Acute chest syndrome of sickle cell disease: genetics, risk factors, prognosis and management

IntroductionSickle cell disease, one of the world's most prevalent Mendelian disorders, is a chronic hemolytic anemia punctuated by acute vasoocclusive events. Both hemolysis and vasoocclusion lead to irreversible organ damage and failure. Among the many sub-phenotypes of sickle cell disease is the acute chest syndrome (ACS) characterized by combinations of chest pain, cough, dyspnea, fever, abnormal lung exam, leukocytosis, hypoxia, and new radiographic opacities. ACS is a major cause of morbidity and mortality.Area coveredWe briefly review the diagnosis, epidemiology, etiology, and current treatments for ACS and focus on understanding and estimating the risks for developing this complication, how prognosis and outcomes might be improved and the genetic elements that might impact the risk of ACS.Expert opinionThe clinical heterogeneity of ACS has hindered our understanding of risk stratification. Lacking controlled clinical trials most treatment is based on expert opinion. Fetal hemoglobin levels and coexistent α thalassemia affect the incidence of ACS; other genetic associations are tenuous. Transfusions, whose use not innocuous, should be targeted to the severity and likelihood of ACS progression. Stable, non-hypoxic patients with favorable hematologic and radiographic findings usually do not need transfusion; severe progressive ACS is best managed with exchange transfusion.